Tumor cells carried in the ascitic form in rats will be studied in vitro for their chemotactic responsiveness to factors generated in rat serum. Reactants necessary for the generation of chemotactic factors as well as the chemotactic factor itself will be purified and characterized. Comparisons and contrasts in chemotactic responses of tumor cells and leukocytes will be made. A combination of in vitro chemotactic assays and protein purification procedures (using ultracentrifugation, electrophonetic, ion exchange and gel filtration methods) will be used. In addition, the ability of chemotactic factors to induce the accumulation of circulating tumor cells will be tested in vivo.